Correction of fabricated shapes in additive manufacturing using modified edge

ABSTRACT

A method of fabricating a polishing pad using an additive manufacturing system includes depositing successive layers by droplet ejection to form the polishing pad. The polishing pad includes a polishing surface having one or more partitions separated by one or more grooves. Depositing a layer of the successive layers includes dispensing first regions corresponding to edges of the one or more partitions by a first droplet ejection process. After curing the first regions, a second region corresponding to interior of the one or more partitions is dispensed between the edges by a different second droplet ejection process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Application Ser. No.62/511,276, filed on May 25, 2017, the entire disclosure of which isincorporated by reference.

TECHNICAL FIELD

This specification relates to additive manufacturing, particularlyadditive manufacturing of chemical mechanical polishing pads.

BACKGROUND

An integrated circuit is typically formed on a substrate by thesequential deposition of conductive, semiconductive, or insulativelayers on a silicon wafer. A variety of fabrication processes requireplanarization of a layer on the substrate. For certain applications,e.g., polishing of a metal layer to form vias, plugs, and lines in thetrenches of a patterned layer, an overlying layer is planarized untilthe top surface of a patterned layer is exposed. In other applications,e.g., planarization of a dielectric layer for photolithography, anoverlying layer is polished until a desired thickness remains over theunderlying layer.

Chemical mechanical polishing (CMP) is one accepted method ofplanarization. This planarization method typically requires that thesubstrate be mounted on a carrier head. The exposed surface of thesubstrate is typically placed against a rotating polishing pad. Thecarrier head provides a controllable load on the substrate to push itagainst the polishing pad. A polishing liquid, such as slurry withabrasive particles, is typically supplied to the surface of thepolishing pad.

One objective of a chemical mechanical polishing process is polishinguniformity. If different areas on the substrate are polished atdifferent rates, then it is possible for some areas of the substrate tohave too much material removed (“overpolishing”) or too little materialremoved (“underpolishing”). In addition to planarization, polishing padscan be used for finishing operations such as buffing.

Polishing pads are typically made by molding, casting or sinteringpolyurethane materials. In the case of molding, the polishing pads canbe made one at a time, e.g., by injection molding. In the case ofcasting, the liquid precursor is cast and cured into a cake, which issubsequently sliced into individual pad pieces. These pad pieces canthen be machined to a final thickness. Grooves can be machined into thepolishing surface, or be formed as part of the injection moldingprocess.

SUMMARY

The present disclosure describes manufacturing polishing pads with anadditive manufacturing system.

In one aspect, a method of fabricating a polishing pad using an additivemanufacturing system includes receiving data indicative of a desiredshape of the polishing pad to be fabricated by droplet ejection by theadditive manufacturing system. The data includes a desired shapedefining a desired profile including a polishing surface having one ormore partitions separated by one or more grooves on the polishing pad.Data indicative of distortions from the desired profile caused bydispensing of layers by droplet ejection by the additive manufacturingsystem is generated. Data indicative of an initial layer to dispense bydroplet ejection is generated to at least partially compensate for thedistortions from the desired profile. The initial layer is dispensed ona support by droplet ejection. Overlying layers are dispensed on theinitial layer by droplet ejection by the additive manufacturing systemto form the polishing pad.

Implementations may include one or more of the following features. Thepolishing pad may include the initial layer. The polishing pad mayinclude the support. The polishing pad may be removed from the support.The distortions may include regions expected to be thin relative to thedesired profile. The initial layer may include voxels corresponding tothe regions. The regions may correspond to edges of the one or morepartitions.

In another aspect, a method of fabricating a polishing pad using anadditive manufacturing system includes depositing successive layers bydroplet ejection to form the polishing pad. The polishing pad includes apolishing surface having one or more partitions separated by one or moregrooves. Depositing a layer of the successive layers includes dispensingfirst regions corresponding to edges of the one or more partitions by afirst droplet ejection process. After curing the first regions, a secondregion corresponding to interior of the one or more partitions isdispensed between the edges by a different second droplet ejectionprocess.

Implementations may include one or more of the following features.

The first droplet ejection may dispense droplets of a first compositionand the second droplet ejection process may dispense droplets of adifferent second composition. One or more portions of the plurality ofsuccessive layers formed of the first composition may be removed. Thefirst droplet ejection process may include a first polymer and thesecond droplet ejection process may include a second polymer ofdifferent composition. The first droplet ejection process may include afirst curing radiation and the second droplet ejection process mayinclude a second curing radiation that cures the layer slower than thefirst curing radiation. The first curing radiation and the second curingradiation may be at different wavelengths. The first curing radiationmay have a higher intensity than the second curing radiation.

Droplets need not be ejected into regions corresponding to the grooves.Depositing the plurality of successive layers may include depositing aninitial layer on a support. The polishing pad may be removed from thesupport, or the polishing pad may include the support. A plurality ofunderlying layers may be dispensed onto a support before dispensing theplurality of successive layers, and the plurality of successive layersmay be dispensed onto the plurality of underlying layers.

In another aspect, a computer program product includes a computerreadable medium encoded with instructions to cause one or moreprocessors to receive data indicative of a desired shape of a polishingpad to be fabricated by droplet ejection by an additive manufacturingsystem, the polishing pad comprising a polishing surface having one ormore partitions separated by one or more grooves, determine from thedata first regions corresponding to edges of the partitions and secondregions corresponding to interior portions of the partitions, and causethe additive manufacturing system to deposit a plurality of successivelayers by droplet ejection to form the polishing pad. The instructionsto deposit the plurality of successive layers include instructions tocause the additive manufacturing system to dispense the first regions bya first droplet ejection process, and after curing the first regions,dispense the second regions by a different second droplet ejectionprocess.

Implementations may include one or more of the following features.

The instructions to dispense by the first droplet ejection process mayinclude instructions to cause the additive manufacturing system todispense droplets of a first composition and the instructions todispense by the second droplet ejection process may include instructionsto cause the additive manufacturing system to dispense droplets of adifferent second composition. The instructions to dispense by the firstdroplet ejection process may include instructions to cause the additivemanufacturing system to cure the first region with a first curingradiation and the instructions to dispense by the second dropletejection process may include instructions to cause the additivemanufacturing apparatus to cure the second region with a secondradiation that cures the layer slower than the first curing radiation.

The instructions to determine first regions corresponding to edges ofthe partitions may include instructions to determine first regionsoutside and abutting a perimeter of the partitions. The instructions todetermine first regions corresponding to edges of the partitions mayinclude instructions to determine first regions inside and abutting aperimeter of the partitions.

In another aspect, an additive manufacturing system includes a support,at least one dispenser configured to deliver a plurality of layers of apad precursor material onto the support by droplet ejection, at leastone energy source, and a controller. The controller is configured toreceive data indicative of a desired shape of a polishing pad to befabricated by droplet ejection by an additive manufacturing system, thepolishing pad comprising a polishing surface having one or morepartitions separated by one or more grooves, and cause the at least onedispenser and at least one energy source to deposit a plurality ofsuccessive layers by droplet ejection and cure the plurality ofsuccessive layers to form the polishing pad. The controller isconfigured to cause the at least one dispenser and the at least oneenergy source to, for each layer of a plurality of layers thatcorrespond to the one or more partitions, dispense and cure firstregions that correspond to edges of the partitions by a first dropletejection and curing process and after curing the first regions dispenseand cure second regions that correspond to interiors of the partitionsby a different second droplet ejection and curing process.

Implementations may include one or more of the following features.

The at least one dispenser may include one or more first nozzles coupledto a first source of a first material of a first composition and one ormore second nozzles coupled to a second source of a second material of adifferent second composition, and the controller may be configured tocause the first nozzles to dispense the first material to the firstregions and cause the second nozzles to dispense the second material tothe second regions.

The at least one energy source may include a first energy source togenerate a first radiation to cure the first region and a second energysource to generate a second radiation to cure the second region. Thefirst radiation may have a different wavelength or intensity than thesecond radiation. The at least one energy source may include a commonenergy source to cure the first region and the second region, and thecontroller may be configured to drive the common energy source at afirst power to generate a first radiation to cure the first region andto drive the common energy source at a second power to generate a secondradiation to cure the second region. The first radiation may have adifferent intensity than the second radiation.

In another aspect, a method of fabricating an object using an additivemanufacturing system includes depositing a plurality of successivelayers by droplet ejection to form the object, the object comprising asurface having one or more protrusions separated by one or morerecesses. Depositing a layer of the successive layers includesdispensing first regions corresponding to edges of the one or moreprotrusions by a first droplet ejection process, and after curing thefirst regions, dispensing a second region corresponding to an interiorof the one or more protrusions between the edges by a different seconddroplet ejection process.

In another aspect, a method of fabricating a polishing pad using anadditive manufacturing system includes depositing a first set ofsuccessive layers onto a support by droplet ejection. Depositing thefirst set of successive layers includes dispensing a polishing padprecursor to first regions corresponding to partitions of the polishingpad and dispensing a sacrificial material to second regionscorresponding to grooves of the polishing pad. A second set ofsuccessive layers is deposited by droplet ejection over the first set ofsuccessive layers. The second set of successive layers corresponds to alower portion of the polishing pad. The first set of successive layerand the second set of successive layers provide a body. The body isremoved from the support. Removing the sacrificial material from thebody provides the polishing pad with a polishing surface that has thepartitions separated by the grooves.

Implementations may include one or more of the following features.Depositing the second set of successive layers may include dispensingthe polishing pad precursor. The second set of successive layers maycorrespond to a lower portion of the polishing layer. A third set ofsuccessive layers may be deposited by droplet ejection over the secondset of successive layers. The third set of successive layers may have adifferent composition than the second set of successive layers. Thesecond set of successive layers may correspond to a sub-pad of thepolishing layer. The second set of successive layers may span both thefirst regions and the second regions.

Advantages of the foregoing may include, but are not limited to, thefollowing. The geometry of a polishing pad can be more preciselycontrolled, thereby improving polishing efficacy of the polishing pad.Furthermore, a correction profile can compensate for potentialdistortions by adjusting data that the additive manufacturing apparatususes to form an article, e.g., a polishing pad, rather than removingmaterial after the article has been initially formed. The amount ofpost-processing of the article after it is formed by the additivemanufacturing apparatus can be decreased. As a result, an amount of feedmaterial waste can be reduced, and yield and throughput can beincreased. The need for a secondary machining step may be eliminated.The change in slurry capture volume of the polishing pad as the surfaceis removed and the groove depth decreases may be reduced, thus improvingwafer-to-wafer uniformity. The capture material may also be removedthrough a selective etching process to leave only the desired material,which can be beneficial where an optically transparent material used asin the formation of a CMP window and in fixed abrasive, roll format paddesigns.

The details of one or more implementations of the subject matterdescribed in this specification are set forth in the accompanyingdrawings and the description below. Other potential features, aspects,and advantages will become apparent from the description, the drawings,and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a polishing system.

FIG. 2 is a schematic side view of an additive manufacturing apparatus.

FIG. 3A is a top view of an example of a polishing pad.

FIG. 3B is a side view of the polishing pad of FIG. 3A.

FIG. 4 is a flowchart of a process to form an article.

FIG. 5 illustrates an example of an actual shape formed based on adesired shape.

FIG. 6 illustrates an actual shape formed based on modification of thedesired shape of FIG. 5.

FIG. 7 illustrates another example of an actual shape formed based on adesired shape.

FIGS. 8A-8D are side view representations of an example pattern andmethod for depositing.

FIGS. 9A-9E are side view representations of an example pattern andmethod for depositing.

FIG. 10 is a schematic side view of another implementation of anadditive manufacturing apparatus.

FIG. 11A is a schematic side view of another implementation of anadditive manufacturing apparatus.

FIG. 11B is a schematic side view of another implementation of anadditive manufacturing apparatus.

FIG. 12 is a schematic side view of another implementation of anadditive manufacturing apparatus.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

An additive manufacturing apparatus can be used to form a polishing pad.The additive manufacturing apparatus can be provided with an initialpattern to dispense feed material. The initial pattern corresponds to adesired shape of the polishing pad to be formed. Unfortunately, when thepolishing pad is formed by the additive manufacturing apparatus usingthe initial pattern, an actual shape of the polishing pad may includedistortions relative to the desired shape of the polishing pad. However,several techniques can be used to compensate for such distortions.

The initial pattern provided to the additive manufacturing apparatus canbe modified by a correction profile to generate a modified pattern to atleast partially compensate for these distortions. The resulting shapeformed using the modified pattern can thus more closely match thedesired shape of the polishing pad. The modified pattern can include aninitial layer onto which additional layers are deposited.

Portions of the polishing pad corresponding to the edges of thepartitions can be a deposited by a different technique than a center ofthe partitions, e.g., to provide improved verticality of side walls.

A sacrificial material can be deposited, and layers of the pad can bedeposited between and over the sacrificial. This sacrificial materialcan then be removed to provide the grooves, surface texture to reducebreak-in times, and to manufacture a polishing pad in a roll-to-rollformat.

Turning now to FIG. 1, a polishing system 100 includes a polishing pad102 that can be used to polish one or more substrates 104. The polishingsystem 100 can include a rotatable platen 106 on which the polishing pad102 is placed. During a polishing step, a polishing liquid 108, e.g.,abrasive slurry, can be supplied to a polishing surface 103 of polishingpad 102 by a slurry supply port or combined slurry/rinse arm 110. Thepolishing liquid 108 can contain abrasive particles, a pH adjuster, orchemically active components.

The substrate 104 is held against the polishing pad 102 by a carrierhead 112. The carrier head 112 is suspended from a support structure,such as a carousel, and is connected by a carrier drive shaft 114 to acarrier head rotation motor so that the carrier head can rotate about anaxis 116. The relative motion of the polishing pad 102 and the substrate104 in the presence of the polishing liquid 108 results in polishing ofthe substrate 104.

Referring to FIG. 2, in some examples, an additive manufacturingapparatus 120 that dispenses successive layers of feed material can beused to form the polishing pad 102. Referring to FIGS. 1 and 2, theadditive manufacturing apparatus 120 is operated to form at least apolishing layer 122 of the polishing pad 102. In the manufacturingprocess, thin layers of feed material are progressively dispensed andcured. For example, droplets 124 of feed material, e.g., polishing padprecursor material, can be ejected from a nozzle 126 of a dispenser 128,e.g., a droplet ejector printer, to form a layer 130 of the feedmaterial. The dispenser 128 is similar to an inkjet printer, but usesthe feed material for forming the polishing pad 102 rather than ink.

A controller 129 is operable to control dispensing operations of thedispenser 128 and, if applicable, control curing operations using anenergy source 131 such as a lamp or a laser. The nozzle 126 istranslated (shown by arrow A) across a support 134 to dispense feedmaterial at any portion of a build area on the support 134.

In some implementations, the energy source 131 trails the nozzle 126 asthe nozzle 126 is translated across the support 134, such that feedmaterial dispensed through the nozzle 126 can be immediately cured. Insome implementations, the energy source 131 leads the nozzle 126 as thenozzle 126 is translated across the support 134 in a first scanningdirection while dispensing feed material. The energy source 131 can curethis dispensed feed material as the energy source 131 is scanned acrossthe support 134, e.g., in a second scanning direction opposite the firstscanning direction, thereby providing the feed material additional timeto reach a stable state before being exposed to radiation of the energysource 131. In some implementations, the energy source 131 leads thenozzle 126 as the nozzle 126 is translated across the support 134 in afirst scanning direction, and the energy source 131 is used to cure thedispensed feed material as the energy source is scanned in the firstscanning direction. Thus, the previously dispensed layer of feedmaterial can be cured almost immediately before another layer isdispensed through the nozzle 126. In some implementations, there aremultiple energy sources, with an energy source 131 that trails thenozzle 126 and an energy source 131 that leads the nozzle 126.

For a first layer 130 a deposited, the nozzle 126 can eject the feedmaterial onto the support 134. For subsequently deposited layers 130 b,the nozzle 126 can eject onto already solidified feed material 132.After each layer 130 is solidified, a new layer is then deposited overthe previously deposited layer until the full 3-dimensional polishinglayer 122 is fabricated. Each layer is applied by the nozzle 126 in apattern stored in a 3D drawing computer program that runs on a computer.Each layer 130 is less than 50% of the total thickness of the polishinglayer 122, e.g., less than 10%, e.g., less than 5%, e.g., less than 1%.

The polishing layer 122 can be formed on a support 134. In someexamples, the support 134 includes a rigid base, or includes a flexiblefilm, e.g., a layer of polytetrafluoroethylene (PTFE). If the support134 includes a flexible film, then the support 134 forms a portion ofthe polishing pad 102. For example, the support 134 can include abacking layer 136 (shown in FIG. 1) of the polishing pad 102 or a layerbetween the backing layer and the polishing layer 122. If the support134 includes the backing layer 136 of the polishing pad 102, the support134 is not removed from the polishing pad 102 after manufacturing of thepolishing pad 102 is complete. Referring to FIG. 1, the polishing pad102 is mounted to the polishing system 100 with the backing layer 136(e.g., the support 134) facing the rotatable platen 106.

If the support 134 does not include the backing layer 136 of thepolishing pad 102, the polishing layer 122 can be removed from thesupport 134 after manufacturing of the polishing pad 102 is complete. Insome implementations, the support 134 can include a rigid base that iscovered by a protective film. The polishing pad 102 can be fabricated onthe protective film. Thereafter, the protective film can be replaced onthe rigid base, and a new polishing pad fabricated on the new protectivefilm. The protective film can be removed from the polishing pad, e.g.,the protective film can remain on the rigid base as the polishing pad isremoved, or the protective film can detach from the rigid base and thenbe peeled off the polishing pad.

Solidification of the layers 130 of feed material can be accomplished bypolymerization. For example, the layer 130 of feed material can be amonomer, and the monomer can be polymerized in-situ by ultraviolet (UV)curing. The feed material can be cured effectively immediately upondepositing, or an entire layer 130 of pad precursor material can bedeposited and then the entire layer 130 be cured simultaneously.Alternatively, the droplets 124 can be a polymer melt that solidifiesupon cooling. In further implementations, the apparatus 120 creates thepolishing layer 122 by spreading a layer of powder and ejecting dropletsof a binder material onto the layer of powder. In this case, the powdercould include additives, e.g., abrasive particles.

In some implementations, the backing layer 136 can also be fabricated bya 3D printing process. For example, the backing layer 136 and polishinglayer 122 could be fabricated in an uninterrupted operation by theapparatus 120. The backing layer 136 can be provided with a differenthardness than the polishing layer 122 by using a different amount ofcuring, e.g., a different intensity of UV radiation, or by using adifferent material. In other implementations, the backing layer 136 isfabricated by a conventional process and then secured to the polishinglayer 122. For example, the polishing layer 122 can be secured to thebacking layer 136 by a thin adhesive layer, e.g., as apressure-sensitive adhesive.

In some implementations, referring to FIGS. 2, 3A, and 3B, when thepolishing layer 122 is formed, the apparatus 120 can selectivelydispense and/or selectively cure portions of the feed material to formgrooves 138 in the polishing layer 122. The grooves 138 can carry thepolishing liquid 108 (shown in FIG. 1). The grooves 138 may be of nearlyany pattern, such as concentric circles, straight lines, cross-hatching,spirals, and the like. Assuming grooves are present, partitions 140between the grooves 138 define the polishing surface 103. The polishingsurface 103, e.g., including the partitions 140 between the grooves 138,can be about 25-90%, e.g., 70-90%, of the total horizontal surface areaof the polishing pad 102. Thus, the grooves 138 can occupy 10%-75%,e.g., 10-30%, of the total horizontal surface area of the polishing pad102. The partitions between the grooves 138 can have a lateral width ofabout 0.1 to 2.5 mm.

Referring to examples illustrated in FIGS. 3A and 3B, in someimplementations, the grooves 138 include concentric circular grooves.These grooves 138 can be uniformly spaced with a pitch P. The pitch P isthe radial distance between adjacent grooves 138. The partitions 140between the grooves 138 have a width W_(p). Each groove 138 are definedby side walls 142 extending from a bottom surface 144 of the groove 138and terminate in at the polishing surface 103, e.g., at the partition140. Each groove 138 may have a depth D_(g) and a width W_(g).

The side walls 142 can extend downwardly from and be generallyperpendicular to the polishing surface 103. In this regard, the sidewalls are substantially perpendicular to the layers 130 of feed materialdispensed on the support 134. In addition, the partitions 140 extendsubstantially parallel to the layers 130 of feed material dispensed onthe support 134.

Each polishing cycle results in wear of polishing pad 102, generally inthe form of thinning of the polishing pad 102 as the polishing surface103 is worn down. The width W_(g) of a groove with substantiallyperpendicular side walls 142 does not change as the polishing pad isworn. Thus, the generally perpendicular side walls 142 ensure that thepolishing pad 102 has a substantially uniform surface area over itsoperating lifetime. As described herein, the manufacturing process toform the polishing pad 102 can include compensatory operations toprevent the polishing surface 103 from being nonplanar, e.g., to ensureplanarity or flatness of the polishing surface 103, and to fabricate theside walls 142 as perpendicular to the polishing surface 103.

The grooves 138 can have a minimum width W_(g) of about 0.34 mm. Eachgroove 138 can have a width W_(g) between 0.34 mm and 2.71 mm, e.g.,between about 0.38 mm and 1.02 mm. Specifically, the grooves 138 mayhave a width W_(g) of approximately 0.51 mm or 0.68 mm. The pitch Pbetween the grooves 138 may be between about 0.68 and 6.10 mm, e.g.,between about 2.29 mm and 5.40 mm. Specifically, the pitch may beapproximately 2.03 or 3.05 mm. Each partition 140 between the grooves138 may have a width W_(p) of at least 0.34 mm. The ratio of groovewidth W_(g) to partition width W_(p) may be selected to be between about0.10 and 0.4. The ratio may be approximately 0.2 or 0.3.

In some implementations, if the polishing pad 102 includes the backinglayer 136, the grooves 138 can extend entirely through the polishinglayer 122. In some implementations, the grooves 138 can extend throughabout 20-80%, e.g., 40%, of the thickness of the polishing layer 122.The depth D_(g) of the grooves 138 can be 0.25 to 1 mm. The polishinglayer 122 can have a thickness T between about 1 mm and 3 mm. Thethickness T should be selected so that the distance D_(p) between thebottom surface 144 of the groove 138 and the backing layer 136 isbetween about 0.5 mm and 4 mm. Specifically, the distance D_(p) may beabout 1 or 2 mm.

Referring to FIG. 4, a manufacturing process 200 to form the polishingpad 102 is illustrated. For example, the additive manufacturingapparatus 120, including the controller 129, can perform operations themanufacturing process 200.

Data indicative of a desired shape of the polishing pad 102 to befabricated is received (202). Data indicative of shapes, including thedata indicative of the desired shape, can be defined by atwo-dimensional or three-dimensional bitmap. For example, each bit canindicate whether material should be present in a corresponding voxel inthe object. In some implementations, the shape data includes datarepresenting a computer-aided design (CAD) model. For example, if theshape data corresponds to the data indicative of the desired shape, theCAD model can be representative of the polishing pad 102 to befabricated.

In some examples, referring to FIG. 5, the desired shape includes adesired feature 300. Absent further manipulation of the data indicativeof the desired shape, when the additive manufacturing apparatus 120forms the desired shape, e.g., dispenses the feed material and cures orallows the feed material to cure to form the desired shape, an actualfeature 310 may be formed based on the data indicative of the desiredshape including the desired feature 300. For example, to form therectangular desired feature 300, the dispenser 128 is controlled todispense parallel layers 130 of feed material. For each layer, aselected portion of feed material having a uniform width correspondingto a width of the rectangular desired feature 300 is cured. Therecesses, e.g., grooves, can be provided by simply not dispensing anyfeed material into the corresponding regions on the object, e.g., thepolishing pad.

During this dispensing and curing process, material properties of thefeed material and the depositing technique of the additive manufacturingapparatus 120 can cause edges of the actual feature 310 to becomeundesirably rounded or beveled. In particular, if the layers 130 of feedmaterial are dispensed in accordance to an original pattern determinedbased on the data indicative of the desired shape, the resulting shapeincludes rounding or beveling as depicted with respect to the actualfeature 310.

For example, as shown in FIG. 5, while a top surface 302 of the desiredfeature 300 is planar, a corresponding top surface 312 of the actualfeature 310 is nonplanar. Due to a beveling effect on the top surface312, lateral edges 304 a, 304 b of the desired feature 300 have agreater length than actual lateral edges 314 a, 314 b of the actualfeature formed by the additive manufacturing apparatus 120. The desiredfeature 300 can correspond to the partitions 140 between the grooves 138(shown in FIGS. 3A and 3B). In this regard, the rounding or bevelingeffect on the top surface 312 can cause the polishing surface 103defined by the partitions 140 to become nonplanar. Without being limitedto any particular theory, the liquid droplets of feed material, e.g.,the liquid pad precursor material, ejected onto the previously depositedlayer can spread and run down the sides of the feature 300, e.g., due towetting, resulting in the rounding.

Referring back to FIG. 4, data indicative of the distortions from thedesired profile (caused by a dispensing of multiple layers by dropletejection by the additive manufacturing system) is generated (204). Thatis, an expected distortion profile is produced. To reduce the roundingor beveling effect (that which is predicted with the expected distortionprofile), the data indicative of the desired shape can be modified. Inthis regard, data indicative of a modified pattern of dispensing feedmaterial to compensate for polishing pad distortions is generated orreceived (206). The distortions include distortions of the polishingsurface 103 of the polishing pad 102. These distortions, in some cases,are caused by the additive manufacturing apparatus 120, as describedherein. The modified pattern differs from the original pattern ofdispensing the feed material in that the modified pattern accounts forthe distortions in the actual feature 310 relative to the desiredfeature. In this regard, in some implementations, the data indicative ofthe modified pattern is determined based on relative differences betweenthe actual feature 310 and the desired feature 300.

For example, as shown in FIG. 6, the data indicative of the modifiedshape includes data indicative of a modified feature 320. Even thoughthe top surface 302 of the desired feature 300 is planar, a top surface322 of the modified feature 320 is nonplanar to compensate for thedistortions of the top surface 312 of the actual feature 310 formed fromthe original pattern. The modified feature 320 is determined based onrelative differences between the desired feature 300 and the actualfeature 310. The top surface 322 of the modified feature 320 is concaveto compensate for the convexity of the top surface 312 of the actualfeature 310. In this regard, the data indicative of the modified shapeis determined based on a combination of the data indicative of thedesired shape and data indicative of the actual shape formed using theoriginal pattern.

Referring back to FIG. 4, an initial layer of the feed material isdispensed by droplet ejection in accordance to a modified pattern (208).A resulting actual feature 330 is formed based on data indicative of themodified pattern to dispense the feed material, the modified patternbeing determined based on the data indicative of the modified shape.

When the dispenser 128 is controlled to dispense the layers 130 of feedmaterial in accordance to the data indicative of the modified pattern(210), a size and shape of a selected portion of the layers 130 of feedmaterial that is cured can vary through a height of the feature. This isin contrast to the process to form the actual feature 310 in which theselected portion of cured feed material is consistent from layer tolayer because the width of the desired feature 300 is consistent fromlayer to layer.

The modified feature 320 includes a concave portion 326 having a widththat varies from layer to layer. A modified pattern to dispense the feedmaterial to form the concave portion 326 differs from the correspondingportion of the original pattern to form the top portion of the desiredfeature 300 in that the selected cured portions of the layers 130 offeed material for the modified pattern have varying widths and shapes.These varying widths and shapes compensate for the distortions presentin the actual feature 310 such that the resulting actual feature 330formed using the modified pattern has reduced convexity compared to theactual feature 310 formed using the original pattern. For example, a topsurface 332 of the actual feature 330 has increased planarity andflatness compared to the top surface 312 of the actual feature 310. Byintentionally controlling where feed material is being dispensed andcured, this correction defined by the modified pattern can better matchthe shape of the resulting polishing pad 102 to the original desiredshape for the polishing pad 102.

For example, the controller 129 can receive an initial data object,e.g., a computer aided design (CAD)-compatible file, e.g., a bitmap,that specifies the initial or intended shape of the object tofabricated. The data object can be stored on a non-transitory computerreadable medium. The controller 129 can be programmed to generate amodified data object, e.g., a modified bitmap, that includes a featureto reduce rounding or beveling. The modified data object can be based onthe intended shape as indicated by the initial data object as well asdata indicating variations from the intended shape that are introducedby the additive manufacturing procedure. Thus, when the polishing pad102 is fabricated using the modified data object, e.g., the modifiedbitmap, it more closely matches the desired design.

FIG. 7 illustrates another example of a desired feature 400 and anactual feature 410 formed based on dispensing and curing patternsdetermined in accordance to the data indicative of the desired feature400. In this particular example, the desired feature 400 had a width of680 μm and a height of 500 μm, although other dimensions are appropriatein an implemented process. As illustrated, the actual feature 410 had anon-planar top surface and slanted side walls.

The desired feature 400 is a constant width feature, e.g., the partition140 separating the grooves 138 of the polishing pad 102. A constantwidth of the partitions 140 can improve wafer-to-wafer polishinguniformity. Furthermore, the polishing efficacy of the polishing pad 102can be dependent on planarity of the polishing surface 103. Using theprocesses described herein, data indicative of a modified pattern can begenerated so that the resulting actual feature formed using the modifiedpattern more closely matches the desired feature 400. In particular, themodified pattern corresponds to the original pattern with an additionalcorrection profile determined using processes described herein. Theadditional correction profile compensates for the distortions of theactual feature 410 formed using the original pattern.

The examples of FIGS. 8A-8C are cross-sections of the layers dispensedand cured by the manufacturing apparatus 120. In some implementations,the data indicative of the shapes described herein include bitmaprepresentations of the shapes to be formed or the shapes formed. Eachbit of the bitmap can correspond to a voxel of a feature of thepolishing pad 102 to be formed.

For example, FIG. 8A illustrates first layer 804 to be deposited to formthe desired feature 400. To compensate for distortion, two outer regionsof a partition 806 along two opposite edges of the feature are dispensedand deposited to form a perimeter of the partition 806. The two outerregions can be defined by a first set of voxels 802 a that provide afirst region adjacent the first edge, and second set of voxels 802 bthat provide a second region adjacent the second edge.

As illustrated by FIG. 8B, after curing the first edge 802 a and thesecond edge 802 b, a successive layer 808 is deposited atop the initiallayer 804. The successive layer 808 has sufficient material to fill inthe remaining portion of the partition 806 between the first set ofvoxels 802 a and the second set of voxels 802 b that provide the edges,and deposit an additional layer atop the first set of voxels 802 a andthe second set of voxels 802 b. The concave shape that is formed atleast partially compensates for distortions to the desired featurecaused by the depositing the plurality of successive layers.

As illustrated by FIG. 8C, after depositing a plurality of successivelayers 810, the resulting feature, e.g., the partition 806, can have atop surface 812 with edges 814 that are less subject to rounding and/orother forms of distortion.

The initial data object need not include the initial layer, whereas themodified data object includes the initial layer. In particular, thecontroller can determine the distortions that would occur to the objectbeing fabricated, and then generate the initial layer to compensate forthese distortions. For example, the controller can identify regionsexpected to be thin relative to the desired profile. These regions canbe made thicker by assigning voxels corresponding to the regions to theinitial layer.

Alternatively, the initial data object might include an initial layer,whereas the modified data object includes a modified initial layer. Forexample, regions that are expected to be thin relative to the desiredprofile can be made thicker by modifying voxels corresponding to theregions in the initial layer to deposit more material so as to make theinitial layer thicker in those regions.

In some implementations, the second layer 808 can be formed by adifferent, second droplet ejection process. For example, the first layer804 can be formed by ejection of droplets of a first composition and thesecond layer can be formed by ejection of droplets of a different secondcomposition. For example, the first material can be a first polymer,whereas the second layer 808 can be a second polymer. The first materialcan be a composition that cures faster than the second material inotherwise similar environmental conditions.

As another example, depositing the first layer 804 can include applyinga first curing radiation to the first layer 804, whereas depositing thesecond layer 808 can include applying second curing radiation that curesthe second layer 808 slower than the first curing radiation cures thefirst layer 804. In some implementations, the first curing radiation andthe second curing radiation have different wavelengths, differentintensities, or different delays between ejection of the droplet andapplication of the respective curing radiation.

Although FIGS. 8A-8C illustrate the first layer 804 as depositeddirectly on the support 134, as shown in FIG. 8D, the first layer 804could be formed over a plurality of layers 820 that form the body of theobject being fabricated, e.g., the main body of the polishing pad. Inthis case, the first layer 820 is the first layer of the feature, e.g.,the partition, that projects above the main body. In this case, thelayer 804 still is located at the perimeter of the partition 806.

The examples of FIGS. 9A-9C are cross-sections of the layers dispensedand cured by the additive manufacturing apparatus 120. In someimplementations, the data indicative of the shapes described hereininclude bitmap representations of the shapes to be formed or the shapesformed. Each bit of the bitmap can correspond to a voxel of a feature ofthe polishing pad 102 to be formed.

For example, FIG. 9A illustrates first layer 904 to be deposited to formthe desired feature 400. To compensate for distortion, two outerregions, including a first region adjacent the first edge and a secondregion adjacent the second edge, are dispensed and deposited to form aperimeter of a partition 906. A first set of voxels 902 a can providethe first region and a second set of voxels 902 b can provide the secondregion.

As shown in FIG. 9B, after curing the first set of voxels 902 a and thesecond set of voxels 902 b, a third set of voxels 908 is depositedbetween the boundary formed by the first layer 904. That is, thesuccessive layer 908 has sufficient material to fill in the remainingportion of the partition 906 and deposit region between the first set ofvoxels 902 a and the second set of voxels 902 b. In this example, littleto no concave shape is formed. Instead, the edge portions (902 a and 902b) are formed by a process that better maintains verticality of the sidewall. This at least partially compensates for distortions of the actualfeature 410. In effect, the edge portions (902 a and 902 b) serve as awall to retain the remainder of the polishing pad precursor that willform a center portion of the partition 908.

In some implementations, the third set of voxels 908 may be deposited bya different, second droplet ejection process. For example, the first andsecond set of voxels 902 a and 902 b be may be formed using droplets ofa material, such as a first polymer, that cures faster than a material,e.g., a second polymer, used for the droplet that form the third set ofvoxels 908.

In some implementations, depositing the first and second sets of voxels902 a and 902 b can include a first curing radiation, while depositingthe third set of voxels 908 can include a second curing radiation thatcures the third set of voxels 908 slower than the first curing radiationcures first and second sets of voxels 902 a and 902 b. In such animplementation, the first curing radiation and the second curingradiation can be at different wavelengths or different intensities. Theapparatus can include different energy sources, e.g., different UVlights, to provide the different wavelengths or intensities.Alternatively, the same energy source can driven at different powerlevels to provide the different intensities.

As shown in FIG. 9C, this process can be repeated until a plurality ofsuccessive layers 910 are deposited. The edge portions 902 a, 902 bserve to form a wall that provides the vertical outer surface ofpartition 906, with the interior portion of the partition provided bythe third set of voxels 908. Assuming that the capture material is notremoved and provides a part of the polishing pad, then the edge portions902 a, 902 b would be regions inside and abutting a perimeter of thepartitions. The controller can be programmed to determine these regionsfrom a data file.

As shown in FIG. 9D, in some implementations, the capture material,i.e., the material of the first and second set of voxels 902 a and 902b, can be removed, e.g., through a selective etching process. Thisleaves only the material of the third set of voxels 908 remaining. Inthis case, the edge portions 902 a, 902 b would be regions outside andabutting a perimeter of the partitions. Again, the controller can beprogrammed to determine these regions from a data file.

This technique can be advantageous if the third set of voxels 908 areformed of an optically transparent material, e.g., for the formation ofa CMP window. This technique can also be advantageous for fixedabrasive, roll format pad designs. This technique can also be used forsecondary polymer curing of the third set of voxels 908 where thematerials of voxels 902 a and 902 b are used as masks.

In some implementations, at least the center portion of the partition,i.e., the third set of voxels, is subject to a secondary polymer curingprocess. The capture material, i.e., the material of the first andsecond set of voxels 902 a and 902 b, can be removed after the secondarycuring.

Although FIGS. 9A-9C illustrate the layers 910 as deposited directly onthe support 134, as shown in FIG. 9E, the plurality of layers 910 thatprovide the partition can be formed over a plurality of layers 920 thatform the body of the object being fabricated, e.g., the main body of thepolishing pad. In this case, the first layer 904 is the first layer ofthe feature, e.g., the partition, that projects above the main body.

FIG. 10 illustrates an example process depositing a first set ofsuccessive layers 1010 by droplet ejection onto the support 134.Depositing the first set of successive layers 1010 involves dispensing apolishing pad precursor 1008 a from a first ejector 1006 a to first setof regions, such as region 1004 b, corresponding to partitions of thepolishing pad. In addition, depositing the first set of successivelayers 1010 involves dispensing a sacrificial material 1008 b from asecond injector 1006 b to a set of second regions, such as region 1004a, corresponding to grooves of the polishing pad. The first ejector 1006a and the second ejector 1006 b can draw from different feed materialsources. In particular, the sacrificial material 1008 b can be depositedsimultaneously with the pad pre-cursor 1008 a. The simultaneousdepositing allows an entire layer to be deposited with one pass of thefirst ejector 1006 a and the second ejector 1006 b. The sacrificialmaterial 1008 b at least partially reduced the distortion that can occurif the pad-precursor 1008 a is deposited on its own by keeping thedeposited pad pre-cursor 1008 a in place before and during curing.

After the first set of successive layers 1010 is deposited, a secondplurality of successive layers 1012 is deposited by droplet ejectionover the first set of successive layers 1010. The second set ofsuccessive layers 1012 spans both the first regions 1004 b and thesecond regions 1004 a. In some implementations, some or all of thesecond set of successive layers 1012 correspond to a lower portion ofthe polishing layer of the polishing pad and are formed from thepolishing pad pre-cursor 1008 a. In some implementations, some or all ofthe second set of successive layers 1012 are formed to have a differentmaterial composition than the first set of successive layers 1010, andcan correspond to a backing layer, e.g., a sub-pad, of the polishingpad. Such layers can be formed from a different material, e.g., adifferent precursor, or the same precursor can be ejected but treateddifferently, e.g., subjected to more or less curing to provide adifferent degree of polymerization and thus a different hardness.

In this implementation, the polishing pad is manufactured upside down.That is the uppermost layer of deposited material corresponds with abase, or lower portion, of the polishing pad. The first set ofsuccessive layers 1010 and the second set of successive layers 1012provide a body of the polishing pad.

Once depositing of the polishing pad material is complete, the body ofthe polishing pad is removed from the support 134. The sacrificialmaterial 1008 b is removed from the body, e.g., by selectively etchingthe sacrificial material, or by lifting away the body of the polishingpad while the sacrificial material remains on the support, to providethe polishing pad having a polishing surface with partitions separatedby grooves.

In some implementations, a third set of successive layers is depositedby droplet ejection over the second set of successive layers 1012. Thethird set of successive layers can have a different composition than thesecond set of successive layers 1012. The second set of successivelayers 1012 can correspond to a lower portion of the polishing pad (alsoknown as a sub-pad of the polishing layer).

Referring to FIG. 11A, in some implementations the top surface of thesupport 134 includes a texture, e.g., projections 1100, and thepolishing pad precursor 1008 is ejected to fill the space between theprojections so as to generate a complementary texture, e.g., thegrooves, on the polishing pad. In particular, depositing a first set ofsuccessive layers 1110 involves dispensing a polishing pad precursor1108 from an ejector 1106 to form the partitions first set of regions,such as region 1104, corresponding to partitions of the polishing pad.After the first set of successive layers 1110 is deposited, a secondplurality of successive layers 1112 is deposited over the first set ofsuccessive layers 1010. The second set of successive layers 1112 spansboth the first regions 1004 and the projections 1110.

In some implementations, some or all of the second set of successivelayers 1112 correspond to a lower portion of the polishing layer of thepolishing pad and are formed from the polishing pad pre-cursor 1008. Insome implementations, some or all of the second set of successive layers1112 are formed to have a different material composition than the firstset of successive layers 1110, and can correspond to a backing layer,e.g., a sub-pad, of the polishing pad. Such layers from can be formedfrom a different material, e.g., a different precursor, or the sameprecursor can be ejected but treated differently, e.g., subjected tomore or less curing to provide a different degree of polymerization andthus a different hardness.

Referring to FIG. 11B, rather than the texture being formed in thesupport 134, the texture can be provided by a film 1120 that is placedon the support 134. In this case, the polishing pad precursor is ejectedonto the film 1120, and the film 1120 is removed from polishing padafter manufacture.

For any of the various implementations discussed above, instead of thedispenser 128 scanning over the support 134, the support can bemoveable. For example, referring to FIG. 12, support 134 could be acontinuous belt. The belt 134 can be driven by drive wheels 160 that arepowered by one or more actuators to move the belt (as shown by arrow B)to carry the dispensed polishing pad precursor under the energy source131 to cure the precursor to form the polishing pad as a sheet. Althoughonly one dispenser 128 and energy source 131 are shown, there can bemultiple dispensers and energy sources arranged in series along the belt134 such that multiple layers can be formed in succession on the belt toform the full thickness of the polishing pad. The cured polishing padsheet 162 can then be lifted from the belt 134 and wound around areceiving roller 164.

The controller, e.g., the controller 129, can be implemented in digitalelectronic circuitry, or in computer software, firmware, or hardware, orin combinations of them. The controller can include one or more computerprogram products, i.e., one or more computer programs tangibly embodiedin an information carrier, e.g., in a non-transitory machine readablestorage medium or in a propagated signal, for execution by, or tocontrol the operation of, data processing apparatus, e.g., aprogrammable processor, a computer, or multiple processors or computers.A computer program (also known as a program, software, softwareapplication, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a standalone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program can be deployed to be executed on onecomputer or on multiple computers at one site or distributed acrossmultiple sites and interconnected by a communication network.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

The controller 129 and other computing devices part of systems describedcan include non-transitory computer readable medium to store a dataobject, e.g., a computer aided design (CAD)-compatible file thatidentifies the pattern in which the feed material should be formed foreach layer. For example, the data object could be a STL-formatted file,a 3D Manufacturing Format (3MF) file, or an Additive Manufacturing FileFormat (AMF) file. For example, the controller could receive the dataobject from a remote computer. A processor in the controller 129, e.g.,as controlled by firmware or software, can interpret the data objectreceived from the computer to generate the set of signals necessary tocontrol the components of the additive manufacturing apparatus 120 todeposit and/or cure each layer in the desired pattern.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made.

The approach shown in FIG. 6 is to deposit one or more additional layersof feed material to compensate for the height of the feature being lessthan desired. For example, one or more additional layers of feedmaterial can be deposited in regions where rounding or beveling occurs.However, alternatively or in addition, the amount of feed materialdeposited in a layer can compensate for the height feature being lessthan desired. For example, the size of droplets or the number ofdroplets ejected can be increased for voxels located in regions wherethe height feature is less than desired, e.g., where rounding orbeveling occurs.

In some implementations, a distribution of volume of the feed materialis modified depending on a location at which the droplets 124 are to bedispensed. A volume of the droplets 124 of feed material is variedduring the dispensing operation. For example, referring back to FIG. 6,the volume of the droplets 124 for forming edges 322 a, 322 b of thefeature can be less than the volume of droplets 124 for forming theinterior portion 322 c of the feature. The controller 129 determines theappropriate weight for forming the edges 322 a, 322 b and the weight forforming the interior portion 322 c based on the material properties ofthe feed material. The dispenser 128 can dispense less feed material tominimize roll off of the feed material. As the dispenser 128 moves toform the interior portion 322 c of the feature, the volume of dropletsis increased. In some implementations, the volume of the droplets 124define a gradient from the edges 322 a, 322 b to the center of thefeature. Depending on the wetting effect of the feed material, this typeof volume control can be used to modulate an amount of feed materialcured when the energy source 131, if present, is operated. For example,if the energy source 131 is scanned across the support 134 to curedifferent portions of the dispensed feed material, drop volume controlcan allow for less feed material to roll off for each pass of the energysource 131 while injecting more feed material at the edges 322 a, 322 bof the feature to reduce the beveling effect described herein.

In some implementations, multiple types of feed material are dispensed.The additive manufacturing apparatus 120 includes, for example, two ormore dispensers, each dispenser dispensing a different type of feedmaterial. In some cases, a single dispenser, e.g., the dispenser 128,receives multiple types of feed material and dispenses a mixture of themultiple types of feed material. Because properties of a first type offeed material may vary from properties of a second type of feedmaterial, the modification to the original pattern to dispense the firsttype of feed material may include a greater or smaller amount of scalingthan the modification to the original pattern to dispense the secondtype of feed material. Alternatively, if droplet weight is controlled,the weights of the droplets of the first type of feed material can becontrolled to be higher or lower than the weights of the droplets of thesecond type of feed material. In some cases, the size of the droplets ofthe first type of feed material can be controlled to be larger orsmaller than the sizes of the droplets of the second type of feedmaterial.

In some implementations, multiple types of feed material form differentportions of the polishing pad 102, for example, to form the polishinglayer 122 and the backing layer 136, or to form different portions ofthe polishing layer 122, e.g., to provide a polishing layer withpolishing properties that vary laterally across the polishing surface.The second type of feed material can include the first type of feedmaterial with an additive that alters the properties of the second typeof feed material relative to the first type of feed material. Theadditive includes, for example, a surfactant that can adjust propertiesof the uncured feed material, for example, zeta potential,hydrophilicity, etc.

Thickness of each layer of the layers of feed material and size of eachof the voxels may vary from implementation to implementation. In someimplementations, when dispensed on the support 134, each voxel can havea width of, for example, 10 μm to 50 μm (e.g., 10 μm to 30 μm, 20 μm to40 μm, 30 μm to 50 μm, approximately 20 μm, approximately 30 μm, orapproximately 50 μm). Each layer can have a predetermined thickness. Thethickness can be, for example, 1 to 80 μm, e.g., 2 to 40 μm (e.g., 2 μmto 4 μm, 5 μm to 7 μm, 10 μm to 20 μm, 25 μm to 40 μm).

Although the method and apparatus have been described in the context offabrication of a polishing pad, the method and apparatus can be adaptedfor fabrication of other articles by additive manufacturing. In thiscase, rather than a polishing surface, there would simply be a topsurface of the object being fabricated, and there would be recesses inthe top surface. The modified pattern can at least partially compensatefor distortions caused by the additive manufacturing system.

In addition, although the method and apparatus haves been described inthe context of fabrication by droplet ejection, the method apparatus canbe adapted for fabrication by other additive manufacturing techniques,e.g., selective powder dispensing followed by sintering.

Accordingly, other implementations are within the scope of the claims.

What is claimed is:
 1. A method of fabricating a polishing pad using anadditive manufacturing system, the method comprising: depositing aplurality of successive layers by droplet ejection to form the polishingpad, the polishing pad comprising a polishing surface having a pluralityof partitions separated by one or more grooves, each partition includingan interior portion and an edge portion surrounding the interior portionwith edge portions of adjacent partitions separated by a groove of theone or more grooves, and wherein depositing a layer of the successivelayers includes dispensing first regions corresponding to the edgeportions of the plurality of partitions by a first droplet ejectionprocess and not ejecting droplets into third regions corresponding tothe grooves between the edge portions of the adjacent partitions, curingthe first regions, after curing the first regions, dispensing secondregions corresponding to the interior portions of the plurality ofpartitions between the edge portions by a different second dropletejection process; and curing the second regions.
 2. The method of claim1, wherein the first droplet ejection process dispenses droplets of afirst composition and the second droplet ejection process dispensesdroplets of a different second composition.
 3. The method of claim 2,comprising removing one or more portions of the plurality of successivelayers formed of the first composition.
 4. The method of claim 2,wherein the first droplet ejection process comprises a first polymer andthe second droplet ejection process comprises a second polymer ofdifferent composition.
 5. The method of claim 1, wherein the firstdroplet ejection process comprises a first curing radiation and thesecond droplet ejection process comprises a second curing radiation thatcures the layer slower than the first curing radiation.
 6. The method ofclaim 5, wherein the first curing radiation and the second curingradiation are at different wavelengths.
 7. The method of claim 6,wherein the first curing radiation has a higher intensity than thesecond curing radiation.
 8. The method of claim 1, wherein depositingthe plurality of successive layers comprises depositing an initial layeron a support.
 9. The method of claim 8, comprising removing thepolishing pad from the support.
 10. The method of claim 8, wherein thepolishing pad comprises the support.
 11. The method of claim 1,comprising dispensing a plurality of underlying layers onto a supportbefore dispensing the plurality of successive layers, and dispensing theplurality of successive layers onto the plurality of underlying layers.12. A computer program product, comprising a non-transitory computerreadable medium encoded with instructions to cause one or moreprocessors to: receive data indicative of a desired shape of a polishingpad to be fabricated by droplet ejection by an additive manufacturingsystem, the polishing pad comprising a polishing surface having aplurality of partitions separated by one or more grooves, each partitionincluding an interior portion and an edge portion surrounding theinterior portion with edge portions of adjacent partitions separated bya groove of the one or more grooves; determine from the data firstregions corresponding to the edge portions of the plurality ofpartitions and second regions corresponding to interior portions of thepartitions; and cause the additive manufacturing system to deposit aplurality of successive layers by droplet ejection to form the polishingpad, wherein the instructions to cause the additive manufacturing systemto deposit the plurality of successive layers include instructions tocause the additive manufacturing system to dispense the first regionscorresponding to the edge portions of the plurality of partitions by afirst droplet ejection process and not ejecting droplets into thirdregions corresponding to the grooves between the edge portions of theadjacent partitions, curing the first regions; after curing the firstregions, dispense the second regions corresponding to the interiorportions between the edge portions by a different second dropletejection process; and curing the second regions.
 13. The computerprogram product of claim 12, wherein the instructions to dispense by thefirst droplet ejection process comprise instructions to cause theadditive manufacturing system to dispense droplets of a firstcomposition and the instructions to dispense by the second dropletejection process comprise instructions to cause the additivemanufacturing system to dispense droplets of a different secondcomposition.
 14. The computer program product of claim 12, wherein theinstructions to dispense by the first droplet ejection process compriseinstructions to cause the additive manufacturing system to cure thefirst regions with a first curing radiation and the instructions todispense by the second droplet ejection process comprise instructions tocause the additive manufacturing apparatus to cure the second regionswith a second radiation that cures a layer of the plurality ofsuccessive layers slower than the first curing radiation.
 15. Thecomputer program product of claim 12, wherein the instructions todetermine first regions corresponding to edges of the partitionscomprises instructions to determine first regions inside and abutting aperimeter of the partitions.
 16. An additive manufacturing system, thesystem comprising: a support; at least one dispenser configured todeliver a plurality of layers of a pad precursor material onto thesupport by droplet ejection; at least one energy source; and acontroller configured to receive data indicative of a desired shape of apolishing pad to be fabricated by droplet ejection by an additivemanufacturing system, the polishing pad comprising a polishing surfacehaving a plurality of partitions separated by one or more grooves, eachpartition including an interior portion and an edge portion surroundingthe interior portion with edge portions of adjacent partitions separatedby a groove of the one or more grooves; and cause the at least onedispenser and at least one energy source to deposit a plurality ofsuccessive layers by droplet ejection and cure the plurality ofsuccessive layers to form the polishing pad, wherein the controller isconfigured to cause the at least one dispenser and the at least oneenergy source to, for each layer of a plurality of layers thatcorrespond to the plurality of partitions, dispense and cure firstregions that correspond to edge portions of the plurality of partitionsby a first droplet ejection and curing process without ejecting dropletsinto third regions corresponding to the grooves between the edgeportions of the adjacent partition and after curing the first regionsdispense and cure second regions that correspond to interiors of thepartitions between the edge portions by a different second dropletejection and curing process.
 17. The system of claim 16, wherein the atleast one dispenser comprises one or more first nozzles coupled to afirst source of a first material of a first composition and one or moresecond nozzles coupled to a second source of a second material of adifferent second composition, and the controller is configured to causethe first nozzles to dispense the first material to the first regionsand cause the second nozzles to dispense the second material to thesecond regions.
 18. The system of claim 16, wherein the at least oneenergy source comprises a first energy source to generate a firstradiation to cure the first regions and a second energy source togenerate a second radiation to cure the second regions, wherein thefirst radiation has a different wavelength or intensity than the secondradiation.
 19. The system of claim 16, wherein the at least one energysource comprises a common energy source to cure the first regions andthe second regions, and the controller is configured to drive the commonenergy source at a first power to generate a first radiation to cure thefirst regions and to drive the common energy source at a second power togenerate a second radiation to cure the second regions, wherein thefirst radiation has a different intensity than the second radiation.